阅读说明：本技术 混合动力汽车发动机转速模式下失火诊断方法及电子设备 (Misfire diagnosis method under engine speed mode of hybrid electric vehicle and electronic equipment ) 是由 秦龙 王冬 王恺 田丰民 柳丛彦 于 2021-07-22 设计创作，主要内容包括：本发明涉及混合动力控制领域,尤其涉及混合动力汽车发动机转速模式下失火诊断方法及电子设备。在发动机转速闭环调控模式下,通过ISG扭矩和扭矩变化率来补偿失火评价相关系数,充分考虑了ISG扭矩对转速调控的影响,可提高发动机失火监测的准确性和稳定性,有效保护发动机；同时,通过确定预设监测窗口,可在区分失火和未失火特征最佳的区域内进行失火评价,进一步提高了失火监测的准确性；提出了失火评价时间阈值自学习方法,可根据失火评价时间的变化实时更新失火评价时间阈值,使失火诊断的结果更加准确和可靠。(The invention relates to the field of hybrid power control, in particular to a misfire diagnosis method and electronic equipment under a hybrid electric vehicle engine speed mode. Under the engine rotating speed closed-loop regulation mode, the misfire evaluation correlation coefficient is compensated through the ISG torque and the torque change rate, the influence of the ISG torque on the rotating speed regulation is fully considered, the accuracy and the stability of the engine misfire monitoring can be improved, and the engine is effectively protected; meanwhile, by determining the preset monitoring window, the misfire evaluation can be carried out in the area with the best distinguishing misfire and non-misfire characteristics, and the accuracy of misfire monitoring is further improved; the self-learning method of the misfire evaluation time threshold value is provided, and the misfire evaluation time threshold value can be updated in real time according to the change of the misfire evaluation time, so that the misfire diagnosis result is more accurate and reliable.)

1. A misfire diagnostic method under a hybrid electric vehicle engine speed mode is characterized by comprising the following steps:

when the ISG torque is not reduced and the misfire diagnosis activation condition is met in the rotating speed mode, performing a corresponding misfire diagnosis strategy;

the misfire diagnosis strategy comprises the following steps: determining a preset monitoring window, recording the running time of each cylinder of the engine in the preset monitoring window, compensating the running time based on ISG (integrated starter generator) torque and torque variation rate, then determining misfire evaluation time and a misfire evaluation time threshold value, performing self-learning updating on the misfire evaluation time threshold value when the misfire evaluation time threshold value self-learning condition is met, and finally comparing whether the misfire evaluation time is smaller than the misfire evaluation time threshold value, wherein if yes, the engine does not have a misfire, and if not, the engine has the misfire;

the misfire evaluation time threshold self-learning updating comprises: comparing the misfire evaluation time under the same working condition, recording the times of increasing and decreasing the misfire evaluation time, updating the misfire evaluation time threshold value when the misfire evaluation time threshold value updating condition is met, recording the times of updating the misfire evaluation time threshold value to be increased and the times of updating the misfire evaluation time threshold value to be decreased, simultaneously judging whether the misfire evaluation time threshold value is only increased or only decreased or not, if so, updating the misfire evaluation time threshold value to be increased or only decreased, and if not, updating the misfire evaluation time threshold value to be increased or also decreased.

2. The misfire diagnostic method in engine speed mode of hybrid electric vehicle according to claim 1, characterized by comprising the steps of:

s1, judging whether the ISG torque is reduced or not, specifically judging whether the ISG torque change rate is less than 0Nm/S or not, if yes, the engine does not have fire, and if not, executing a step S2;

s2, judging whether the misfire diagnosis activation condition is satisfied under the rotation speed mode, if so, executing the step S3, and if not, re-executing the step S1;

s3, determining a preset monitoring window, specifically, taking a certain crankshaft angle range near a compression top dead center of each cylinder of the engine, and recording the operation time T of each cylinder of the engine in the preset monitoring window in real time_{n_Raw}Wherein n is the engine cylinder number;

s4, compensating the operation time based on the ISG torque and the torque change rate, specifically calculating the engine is in the pre-operation timeSetting average value M of ISG torque in monitoring window_ISGAnd average value DeltaM of ISG torque change rate_ISGBased on the mean value M of the ISG torque_ISGAnd average value DeltaM of ISG torque change rate_ISGDetermining multiplication factors by performing a calibration look-up tableWill be provided withThe running time of each cylinder of the engine after correction in a preset monitoring window is taken as the running time;

s5, determining the misfire evaluation time, specifically calculating the T of the same cylinder which is twice continuous_nTime difference T_nDiffThen calculating T of two consecutive times of the last combustion cylinder_mTime difference T_mDiffWhere m is the cylinder number of the last combustion cylinder, then T_nDiffTotal＝T_mDiff–T_nDiffNamely the misfire evaluation time of the current combustion cylinder n;

s6, determining a fire evaluation time threshold, specifically calibrating the fire evaluation time threshold under different rotating speeds and loads through a rack under certain water temperature and fire efficiency, and then compensating the fire evaluation time threshold under different water temperatures and loads on an actual vehicle;

s7, judging whether the self-learning condition of the misfire evaluation time threshold value is satisfied, if so, executing a step S8, and if not, executing a step S12;

s8, calculating the average value of the misfire evaluation time under certain working conditions of the engine speed, the load, the ignition angle and the water temperature within a period of time, calculating the average value of the misfire evaluation time of the engine within the same period of time when the engine reaches the working conditions of the same speed, the load, the ignition angle and the water temperature again, comparing the average values of the misfire evaluation time obtained by two adjacent times, and respectively recording the increasing and decreasing times of the misfire evaluation time by using a counter a and a counter b;

s9, judging whether the update condition of the misfire evaluation time threshold is satisfied, specifically comparing the values of a counter a and a counter B, if the value of the counter B is smaller than a preset value C, but the value of the counter a is larger than a preset value D, accumulating the average value of the misfire evaluation time when the misfire evaluation time is increased by multiplying a preset coefficient A to the misfire evaluation time threshold before correction, and clearing the values of the counter a and the counter B, if the value of the counter a is smaller than the preset value E, but the value of the counter B is larger than the preset value F, accumulating the average value of the misfire evaluation time when the misfire evaluation time is decreased by multiplying the preset coefficient B to the misfire evaluation time threshold before correction, and clearing the values of the counter a and the counter B, if the two conditions are not satisfied, not updating the misfire evaluation time threshold, and directly executing the step S12;

s10, recording the number of times the misfire evaluation time threshold value is updated to increase using the counter c, and the number of times the misfire evaluation time threshold value is updated to decrease using the counter d;

s11, judging whether the fire evaluation time threshold value is only increased or only decreased, specifically comparing the values of a counter c and a counter d, if the value of the counter c is larger than the value of the counter d and exceeds a preset value G, the fire evaluation time threshold value is only allowed to be increased, if the value of the counter c is smaller than the value of the counter d and exceeds a preset value H, the fire evaluation time threshold value is only allowed to be decreased, and if the two conditions are not satisfied, the fire evaluation time threshold value is increased or decreased;

and S12, judging whether the misfire evaluation time is smaller than the misfire evaluation time threshold value, if so, judging that the engine has no misfire, and if not, judging that the engine has misfire.

3. The misfire diagnostic method in engine speed mode of hybrid vehicle according to claim 1 or 2, characterized in that: the misfire diagnosis activation condition in the rotation speed mode specifically includes:

1) no fuel cut request;

2) the water temperature of the engine is in a preset range;

3) the fluctuation of the opening degree of the throttle valve is small in the diagnosis process;

4) the engine is in an operating state;

5) the ISG torque precision is within the range of +/-2%;

6) the hybrid electric vehicle is in an engine rotating speed closed-loop control mode;

7) the fluctuation of the engine speed does not exceed the preset speed.

4. The misfire diagnostic method in engine speed mode of hybrid vehicle according to claim 3, characterized in that: the water temperature of the engine is in a preset range, namely, the water temperature of the engine is between 40 ℃ and 105 ℃; the smaller fluctuation of the opening degree of the throttle valve in the diagnosis process is specifically that the difference between the maximum opening degree and the minimum opening degree of the throttle valve within 0.1s is less than 15 percent; the hybrid electric vehicle is in an engine speed closed-loop control mode, specifically, a clutch of the hybrid electric vehicle is disengaged or the clutch is in a process from disengagement to engagement; specifically, the fluctuation of the engine speed does not exceed the preset speed, namely the fluctuation of the engine speed does not exceed +/-15 rpm.

5. The misfire diagnostic method in engine speed mode of hybrid vehicle according to claim 2, characterized in that: average value M of the ISG torque_ISGIs determined by ISG real-time torque value M_ISGRawISG rotation speed S_ISGAnd the rotational speed S of the clutch_ClutchThe common determination is as follows:

in the formula (I), the compound is shown in the specification,for ISG real-time torque value M_ISGRawK is a coefficient, S_ISG(t) and S_Clutch(t) real-time ISG rotational speed and clutch rotational speed, respectively;

average value DeltaM of ISG torque change rate_ISGThe calculation method of (2) is as follows:

in the formula, K is a coefficient,is a real-time value of the ISG torque rate of change,is the sampling step, at is the sampling period,the ISG torque rate of change value of the last sampling period, phi is the engine running angle, S_EngReal-time engine speed;

the multiplication factorIn the formula T_{n0_Raw}And the running time of each cylinder of the engine in the preset monitoring window is the running time when the ISG torque is not loaded under the same engine speed and load.

6. The misfire diagnostic method in engine speed mode of hybrid vehicle according to claim 1 or 2, characterized in that: the self-learning condition of the misfire evaluation time threshold specifically comprises the following steps:

1) no misfire was detected;

2) the ISG does not adjust the rotating speed;

3) the engine is in a running state;

4) the engine has no oil cut;

5) leveling the pavement;

6) the engine speed and the load are stable;

7) the water temperature of the engine is within a preset range.

7. The misfire diagnostic method in engine speed mode of hybrid vehicle according to claim 6, characterized in that: the ISG does not adjust the rotating speed specifically, the ISG torque change rate is less than 0 Nm/s; the engine speed and the load are stable, specifically, the change rate of the engine speed is not more than +/-15 rpm, and the engine load is not more than +/-20 mg/l; the water temperature of the engine is in a preset range, namely, the water temperature of the engine is between 40 ℃ and 105 ℃.

8. The misfire diagnostic method in engine speed mode of hybrid vehicle according to claim 2, characterized in that: when calculating the average value of the fire evaluation time when the fire evaluation time is increased, firstly eliminating the minimum 20 percent and the maximum 20 percent of the numerical values, and then calculating the average value; and when calculating the average value of the misfire evaluation time when the misfire evaluation time is reduced, firstly eliminating the minimum 20 percent and the maximum 20 percent of the numerical values, and then calculating the average value.

9. The misfire diagnostic method in engine speed mode of hybrid vehicle according to claim 2, characterized in that: after the counters a and b are cleared, the counters a and b start counting again from zero; the counters a, b, c, d and the misfire evaluation time threshold value may all be saved electrically down.

10. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein: the processor, when executing the program, performs the steps of the method according to claims 1 to 9.

Technical Field

The invention relates to the field of hybrid power control, in particular to a misfire diagnosis method and electronic equipment under a hybrid electric vehicle engine speed mode.

Background

The traditional fuel vehicle is mainly used for fire diagnosis by monitoring the change of the crankshaft angular velocity, and the principle of the traditional fuel vehicle is mainly that the engine runs stably and the difference of the change of the crankshaft angular velocity is expressed to distinguish and judge when a fire occurs. In a typical P1+ P3 hybrid power configuration, because two completely different transmission modes of series power generation and parallel direct drive exist when an engine runs, an ISG (integrated starting/power generation integrated motor) can play a power assisting role and can also generate power. Therefore, for the crankshaft, the ISG motor will either generate positive torque to drive the crankshaft to rotate or generate negative torque as a load of the crankshaft under different operating conditions. The speed of regulation of the ISG torque is much faster than the speed of regulation of the torque generated by engine combustion.

Under the same engine working condition, namely the engine rotating speed and the torque are kept constant, because the ISG regulation speed is high, under the engine rotating speed closed-loop regulation mode, the regulation and control of the ISG torque can weaken the rotating speed fluctuation caused by the engine fire, and if the existing engine fire diagnosis strategy is adopted, the engine fire misjudgment can be caused because the influence of the ISG torque is not considered.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the method for diagnosing the misfire of the hybrid electric vehicle in the engine rotating speed mode and the electronic equipment can improve the accuracy and stability of the misfire monitoring of the engine in the engine rotating speed closed-loop regulation and control mode, so that the misfire diagnosis result is more reliable.

In order to solve the technical problems, the invention adopts the technical scheme that:

a misfire diagnostic method under a hybrid electric vehicle engine speed mode is characterized by comprising the following steps:

when the ISG torque is not reduced and the misfire diagnosis activation condition is met in the rotating speed mode, performing a corresponding misfire diagnosis strategy;

the misfire diagnosis strategy comprises the following steps: determining a preset monitoring window, recording the running time of each cylinder of the engine in the preset monitoring window, compensating the running time based on ISG (integrated starter generator) torque and torque variation rate, then determining misfire evaluation time and a misfire evaluation time threshold value, performing self-learning updating on the misfire evaluation time threshold value when the misfire evaluation time threshold value self-learning condition is met, and finally comparing whether the misfire evaluation time is smaller than the misfire evaluation time threshold value, wherein if yes, the engine does not have a misfire, and if not, the engine has the misfire;

the misfire evaluation time threshold self-learning updating comprises: comparing the misfire evaluation time under the same working condition, recording the times of increasing and decreasing the misfire evaluation time, updating the misfire evaluation time threshold value when the misfire evaluation time threshold value updating condition is met, recording the times of updating the misfire evaluation time threshold value to be increased and the times of updating the misfire evaluation time threshold value to be decreased, simultaneously judging whether the misfire evaluation time threshold value is only increased or only decreased or not, if so, updating the misfire evaluation time threshold value to be increased or only decreased, and if not, updating the misfire evaluation time threshold value to be increased or also decreased.

Further, the misfire diagnosis method under the engine speed mode of the hybrid electric vehicle specifically comprises the following steps:

s1, judging whether the ISG torque is reduced or not, specifically judging whether the ISG torque change rate is less than 0Nm/S or not, if yes, the engine does not have fire, and if not, executing a step S2;

s2, judging whether the misfire diagnosis activation condition is satisfied under the rotation speed mode, if so, executing the step S3, and if not, re-executing the step S1;

s3, determining a preset monitoring window, specifically, taking a certain crankshaft angle range near a compression top dead center of each cylinder of the engine, and recording the operation time T of each cylinder of the engine in the preset monitoring window in real time_{n_Raw}Wherein n is the engine cylinder number;

s4, compensating the running time based on the ISG torque and the torque change rate, specifically calculating the average value M of the ISG torque of the engine in the preset monitoring window_ISGAnd average value DeltaM of ISG torque change rate_ISGBased on the mean value M of the ISG torque_ISGAnd average value DeltaM of ISG torque change rate_ISGPerforming a calibration lookup to determine multiplicationsFactor(s)Will be provided withThe running time of each cylinder of the engine after correction in a preset monitoring window is taken as the running time;

s5, determining the misfire evaluation time, specifically calculating the T of the same cylinder which is twice continuous_nTime difference T_nDiffThen calculating T of two consecutive times of the last combustion cylinder_mTime difference T_mDiffWhere m is the cylinder number of the last combustion cylinder, then T_nDiffTotal＝T_mDiff–T_nDiffNamely the misfire evaluation time of the current combustion cylinder n;

s6, determining a fire evaluation time threshold, specifically calibrating the fire evaluation time threshold under different rotating speeds and loads through a rack under certain water temperature and fire efficiency, and then compensating the fire evaluation time threshold under different water temperatures and loads on an actual vehicle;

s7, judging whether the self-learning condition of the misfire evaluation time threshold value is satisfied, if so, executing a step S8, and if not, executing a step S12;

s8, calculating the average value of the misfire evaluation time under certain working conditions of the engine speed, the load, the ignition angle and the water temperature within a period of time, calculating the average value of the misfire evaluation time of the engine within the same period of time when the engine reaches the working conditions of the same speed, the load, the ignition angle and the water temperature again, comparing the average values of the misfire evaluation time obtained by two adjacent times, and respectively recording the increasing and decreasing times of the misfire evaluation time by using a counter a and a counter b;

s9, judging whether the update condition of the misfire evaluation time threshold is satisfied, specifically comparing the values of a counter a and a counter B, if the value of the counter B is smaller than a preset value C, but the value of the counter a is larger than a preset value D, accumulating the average value of the misfire evaluation time when the misfire evaluation time is increased by multiplying a preset coefficient A to the misfire evaluation time threshold before correction, and clearing the values of the counter a and the counter B, if the value of the counter a is smaller than the preset value E, but the value of the counter B is larger than the preset value F, accumulating the average value of the misfire evaluation time when the misfire evaluation time is decreased by multiplying the preset coefficient B to the misfire evaluation time threshold before correction, and clearing the values of the counter a and the counter B, if the two conditions are not satisfied, not updating the misfire evaluation time threshold, and directly executing the step S12;

s10, recording the number of times the misfire evaluation time threshold value is updated to increase using the counter c, and the number of times the misfire evaluation time threshold value is updated to decrease using the counter d;

and S11, judging whether the misfire evaluation time threshold value is only increased or only decreased, specifically comparing the values of a counter c and a counter d, if the value of the counter c is greater than the value of the counter d and exceeds a preset value G, updating the misfire evaluation time threshold value is only allowed to be increased, if the value of the counter c is less than the value of the counter d and exceeds a preset value H, updating the misfire evaluation time threshold value is only allowed to be decreased, and if the two conditions are not satisfied, updating the misfire evaluation time threshold value is increased or decreased.

And S12, judging whether the misfire evaluation time is smaller than the misfire evaluation time threshold value, if so, judging that the engine has no misfire, and if not, judging that the engine has misfire.

Further, the misfire diagnosis activation condition in the rotation speed mode specifically includes:

1) no fuel cut request;

2) the water temperature of the engine is in a preset range;

3) the fluctuation of the opening degree of the throttle valve is small in the diagnosis process;

4) the engine is in an operating state;

5) the ISG torque precision is within the range of +/-2%;

6) the hybrid electric vehicle is in an engine rotating speed closed-loop control mode;

7) the fluctuation of the engine speed does not exceed a preset fluctuation value of the engine speed.

Further, the water temperature of the engine is in a preset range, specifically, the water temperature of the engine is between 40 ℃ and 105 ℃; the smaller fluctuation of the opening degree of the throttle valve in the diagnosis process is specifically that the difference between the maximum opening degree and the minimum opening degree of the throttle valve within 0.1s is less than 15 percent; the hybrid electric vehicle is in an engine speed closed-loop control mode, specifically, a clutch of the hybrid electric vehicle is disengaged or the clutch is in a process from disengagement to engagement; the fluctuation of the engine rotating speed does not exceed a preset fluctuation value of the rotating speed, namely the fluctuation of the engine rotating speed does not exceed +/-15 rpm.

Further, an average value M of the ISG torque_ISGIs determined by ISG real-time torque value M_ISGRawISG rotation speed S_ISGAnd the rotational speed S of the clutch_ClutchThe common determination is as follows:

in the formula (I), the compound is shown in the specification,for ISG real-time torque value M_ISGRawK is a coefficient, S_ISG(t) and S_Clutch(t) the ISG rotating speed and the clutch rotating speed at the moment of real time t are respectively;

average value DeltaM of ISG torque change rate_ISGThe calculation method of (2) is as follows:

in the formula, K is a coefficient,is a real-time value of the ISG torque rate of change,is the sampling step, at is the sampling period,the ISG torque rate of change value of the last sampling period, phi is the engine running angle, S_EngReal-time engine speed;

the multiplication factorIn the formula T_{n0_Raw}And the running time of each cylinder of the engine in the preset monitoring window is the running time when the ISG torque is not loaded under the same engine speed and load.

Further, the misfire evaluation time threshold value self-learning condition specifically includes:

1) no misfire was detected;

2) the ISG does not adjust the rotating speed;

3) the engine is in a running state;

4) the engine has no oil cut;

5) leveling the pavement;

6) the engine speed and the load are stable;

7) the water temperature of the engine is within a preset range.

Further, the rotation speed of the ISG is not regulated, specifically, the torque change rate of the ISG is less than 0 Nm/s; the engine speed and the load are stable, specifically, the change rate of the engine speed is not more than +/-15 rpm, and the engine load is not more than +/-20 mg/l; the water temperature of the engine is in a preset range, namely, the water temperature of the engine is between 40 ℃ and 105 ℃.

Further, when calculating the average value of the misfire evaluation time when the misfire evaluation time increases, firstly eliminating the minimum 20% and the maximum 20% of the numerical values, and then calculating the average value; when calculating the average value of the misfire evaluation time when the misfire evaluation time is reduced, the minimum 20 percent and the maximum 20 percent of the numerical values are removed, and then the average value is calculated.

Further, after the counters a and b are cleared, the counters a and b start counting again from zero; the counters a, b, c, d and the misfire evaluation time threshold value may all be saved electrically down.

An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein: the processor implements the steps of the method as described above when executing the program.

Compared with the prior art, the invention has the following main advantages:

1. under the engine rotating speed closed-loop regulation mode, the misfire evaluation correlation coefficient is compensated through the ISG torque and the torque change rate, the influence of the ISG torque on the rotating speed regulation is fully considered, the accuracy and the stability of the engine misfire monitoring can be improved, and the engine is effectively protected;

2. by determining the preset monitoring window, the misfire evaluation can be carried out in the area with the best distinguishing misfire and non-misfire characteristics, and the accuracy of misfire monitoring is further improved;

3. the self-learning method of the misfire evaluation time threshold value is provided, and the misfire evaluation time threshold value can be updated in real time according to the change of the misfire evaluation time, so that the misfire diagnosis result is more accurate and reliable.

Drawings

FIG. 1 is a schematic diagram of a main electric control drive assembly of a hybrid electric vehicle;

FIG. 2 is a logic diagram of a misfire diagnostic method in an engine speed mode of a hybrid electric vehicle according to the present invention.

In the figure: 1. an engine; 2. an integrated starter/generator integrated motor (ISG); 3. a drive motor; 4. a high voltage battery; 5. a clutch.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings 1-2 and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

It should be noted that, according to the implementation requirement, each step/component described in the present application can be divided into more steps/components, and two or more steps/components or partial operations of the steps/components can be combined into new steps/components to achieve the purpose of the present invention.

In the first embodiment, a main electric control driving assembly of a hybrid electric vehicle is shown in fig. 1, and includes an engine 1, an integrated starting/power generation integrated motor (ISG)2, a driving motor 3, a high-voltage battery 4, and a clutch 5.

The ISG is directly connected with the engine for starting, power generation and assistance; the engine and the driving motor output power together, and a clutch is arranged behind the engine and used for switching a transmission state. In a pure electric state, the engine and the ISG motor do not work, and the power battery provides electric energy to drive the motor to drive the vehicle; in a series state, the clutch is disengaged, the engine does not participate in driving the vehicle, and is only responsible for driving the ISG motor to generate power and supply the power to the driving motor to drive the vehicle, and redundant power generation is stored in the power battery; in the parallel state, the clutch is engaged and the engine is used directly to drive the vehicle.

And the engine speed mode is specifically that the engine speed is regulated in a closed loop mode when the clutch of the hybrid electric vehicle is disengaged or the clutch is in the process of disengaging to engaging. In the rotating speed closed-loop regulation and control process, due to the regulation and control of the ISG, the ISG can output torque, and if the torque is a negative value, the torque can be represented as that the engine torque can be increased to charge the ISG; if the torque is positive, it can be characterized as engine torque requiring the ISG to power up, driving the engine for speed stabilization.

The misfire diagnostic method under the engine speed mode of the hybrid electric vehicle implemented according to the invention is shown in FIG. 2 and comprises the following steps:

and S1, judging whether the ISG torque is reduced or not, specifically judging whether the ISG torque change rate is less than 0Nm/S or not, if so, judging that the engine does not have a fire, and if not, executing a step S2.

The ISG torque reduction indicates that the engine speed is not regulated through the ISG at the moment, and no misfire occurs at the moment.

And S2, judging whether the misfire diagnosis activation condition is met in the rotating speed mode, if so, executing step S3, and if not, executing step S1 again.

The misfire diagnosis activation condition in the rotation speed mode specifically includes:

1) no fuel cut request;

2) the water temperature of the engine is within a preset range, specifically the water temperature of the engine is between 40 ℃ and 105 ℃;

3) in the diagnosis process, the fluctuation of the opening degree of the throttle valve is small, and specifically, the difference between the maximum opening degree and the minimum opening degree of the throttle valve within 0.1s is less than 15 percent;

4) the engine is in an operating state;

5) the ISG torque precision is within the range of +/-2%;

6) the hybrid electric vehicle is in an engine speed closed-loop control mode, and particularly, a clutch of the hybrid electric vehicle is disengaged or the clutch is in a process from disengagement to engagement;

7) the fluctuation of the engine speed does not exceed a preset fluctuation value of the engine speed, specifically the fluctuation of the engine speed does not exceed +/-15 rpm.

S3, after the fire diagnosis is allowed to enter, determining a preset monitoring window, and recording the running time T of each cylinder of the engine in the preset monitoring window in real time_{n_Raw}Where n is the engine cylinder number (in this example, the engine is a four-cylinder engine, n may be 0,1,2, 3).

The preset monitoring window is specifically a certain crankshaft angle range near a compression top dead center of each cylinder of the engine, and whether a fire occurs or not is evaluated in the preset monitoring window according to a fire evaluation method. The preset monitoring window aims to find an optimal characteristic region capable of distinguishing the misfire from the non-misfire, whether the engine is on fire or not is evaluated in the optimal region, and the accuracy of engine misfire monitoring can be improved.

S4, compensating the running time based on the ISG torque and the torque change rate, specifically calculating the average value M of the ISG torque of the engine in the preset monitoring window_ISGAnd average value DeltaM of ISG torque change rate_ISGBased on the mean value M of the ISG torque_ISGAnd average value DeltaM of ISG torque change rate_ISGDetermining multiplication factors by performing a calibration look-up tableWill be provided withMonitoring cylinders of engine at preset as modifiedThe runtime of the window.

Wherein the average value M of the ISG torque_ISGIs determined by ISG real-time torque value M_ISGRawISG rotation speed S_ISGAnd the rotational speed S of the clutch 5_ClutchAnd (4) jointly determining. It is mainly considered that the torque generated by the ISG needs to be compensated for engine torque on the one hand and due to torsional disturbances of the ISG and clutch-end drive train linkage on the other hand.

WhereinFor ISG real-time torque value M_ISGRawK is a coefficient, in this example 0.2308r/min is taken, where S_ISG(t) and S_Clutch(t) represents the ISG rotational speed and the clutch rotational speed, respectively, at time t.

Average value of ISG Torque Change Rate DeltaM_ISGThe calculation method of (1) is as follows, in order to ensure the smoothness of the torque change rate:

is an ISG torque change rate real-time value, wherein

The value of the ISG torque rate of the last sampling period, where the sampling period Δ t is 10 ms.

Is the average of the ISG torque rate of change, where K is a coefficient, taken in this example as 0.34(r/min)²。

Further, to determine the sample step size Δ T, the engine angle period over which the torque rate of change is sampled is first determined_phi: for a four-stroke engine, each cylinder completes every 2 revolutions of the engineOne air intake and one air intake cause real change of torque, and sampling calculation based on the engine speed (namely the engine angle) is needed to be more representative of the authenticity of the torque change rate. The maximum engine angle cycle is essentially the average engine operating angle for each cylinder intake stroke, i.e., 720/N, where 720 refers to a crankshaft angle of 2 engine revolutions and N is the number of engine cylinders, and then the average engine operating angle for each cylinder intake stroke is 720/N. In order to further improve the control precision, the sampling period is further refined, but a principle is kept, the engine operation angle phi corresponding to the delta T can be divided by 720 degrees/N, if the sampling period is too small, the operation load rate of a control system is improved, and finally phi is balanced by the requirement of project development precision (in the example, the engine angle period is 4 cylinders, and the engine angle period is too small)_phi is 22.5 deg., then the engine misfire false positive rate and the engine misfire false negative rate are both below 1%).

Based on engine operating angle phi and real-time engine speed S for calculating torque rate of change_Eng(rpm) to determine the sampling step Δ T:

where phi can be divided exactly by 720/N.

Further, the multiplication factorAccording to the initial operation time T of setting the ISG torque and the different torque change rates to different degrees under different rotating speeds_{n_Raw}Running time T when ISG torque is not applied under the same engine speed and load_{n0_Raw}Multiplication factorIs equal to T_{n0_Raw}/T_{n_Raw}。

S5, determining the misfire evaluation time, specifically calculating the T of the same cylinder which is twice continuous_nTime difference T_nDiffThen calculate againT for one combustion cylinder twice in succession_mTime difference T_mDiffWhere m is the cylinder number of the last combustion cylinder, then T_nDiffTotal＝∣T_mDiff–T_nDiff| is the misfire evaluation time of the current combustion cylinder n.

And S6, determining the fire evaluation time threshold according to the engine speed, the load, the water temperature and the ignition efficiency, specifically calibrating the fire evaluation time threshold at different speeds and loads through a rack under certain water temperature and ignition efficiency, and then compensating the fire evaluation time threshold at different water temperatures and loads on the real vehicle.

The misfire evaluation time threshold value is determined by the following method, and the time standard when the misfire (set by the misfire generator) occurs is used as the misfire evaluation time threshold value under the working condition:

under any working condition in the misfire monitoring window area, the calculated values of the misfire time standard when no misfire occurs and the misfire occurs constitute statistical data of S1 and S2 respectively, and assuming that they both satisfy normal distribution, an effective algorithm should satisfy the following condition, namely, triple standard deviation principle.

μ₁And mu₂Average values of misfire time standards under the working condition when no misfire occurs and the misfire occurs are obtained for a large number of data samples (the data samples are not less than 10000) respectively;

σ₁and σ₁And obtaining standard difference values of the misfire time standard under the working condition when no misfire occurs and the misfire time standard when the misfire occurs respectively for a large number of data samples (the data samples are not less than 10000).

And S7, judging whether the self-learning condition of the misfire evaluation time threshold value is satisfied, if so, executing step S8, and if not, executing step S12.

The misfire evaluation time threshold value self-learning condition specifically comprises the following steps:

1) no misfire was detected;

2) the ISG does not adjust the rotating speed, and particularly the ISG torque change rate is less than 0 Nm/s;

3) the engine is in a running state;

4) the engine has no oil cut;

5) leveling the pavement;

6) the engine speed and the load are stable, specifically, the change rate of the engine speed is not more than +/-15 rpm, and the engine load is not more than +/-20 mg/l;

7) the water temperature of the engine is within a preset range, and specifically the water temperature of the engine is between 40 ℃ and 105 ℃.

And S8, calculating the average value of the misfire evaluation time under the working condition of certain rotating speed, load, ignition angle and water temperature of the engine within a period of time (the period of time is 5S in the example), calculating the average value of the misfire evaluation time of the engine within the same period of time (the period of time is 5S in the example) when the engine reaches the working condition of the same rotating speed, load, ignition angle and water temperature again, comparing the average values of the misfire evaluation time obtained in two adjacent times, and respectively recording the increasing and decreasing times of the misfire evaluation time by using a counter a and a counter b.

S9, determining whether the misfire evaluation time threshold value updating condition is satisfied, specifically comparing the values of the counter a and the counter b:

if the value of the counter b is smaller than the preset value C (200 in the present example) but the value of the counter a is larger than the preset value D (2000 in the present example), the average value of the misfire evaluation times when the misfire evaluation time increases is multiplied by a preset coefficient A (0.001 in the present example) and accumulated to the misfire evaluation time threshold value before correction, and the values of the counter a and the counter b are cleared.

When calculating the average value of the misfire evaluation time when the misfire evaluation time increases, the average value of the misfire evaluation time is calculated by eliminating the 20% with the minimum value and the 20% with the maximum value in the misfire evaluation time when the misfire evaluation time increases, and then calculating the average value.

If the value of the counter a is smaller than the preset value E (20 in the present example) but the value of the counter B is larger than the preset value F (200 in the present example), the misfire evaluation time average value at which the misfire evaluation time appears to be reduced is multiplied by a preset coefficient B (0.03 in the present example) to be accumulated to the misfire evaluation time threshold value before correction, and the values of the counter a and the counter B are cleared.

When calculating the average value of the misfire evaluation time when the misfire evaluation time is reduced, eliminating the 20% with the minimum value and the 20% with the maximum value in the misfire evaluation time when the misfire evaluation time is reduced, and then calculating the average value.

Further, the preset coefficient a is not greater than the preset coefficient B, and the preset value C is greater than the preset value E, so calibrated that the misfire is more easily detected when the misfire evaluation time threshold value decreases.

Furthermore, the reason for updating the misfire evaluation time threshold value is that the aging of the components such as the oil injection, the ignition and the air intake of the engine causes unstable combustion of the engine and possibly causes misfire, and a large number of tests show that the aging components have deteriorated working performance, unstable combustion effect and more easily caused misfire probability of the engine, so that the misfire evaluation time threshold value needs to be updated by corresponding preset coefficients.

If neither of the above conditions is satisfied, the misfire evaluation time threshold value is not updated, and step S12 is executed as it is.

After the counter a and the counter b are cleared, the number of times of increasing and decreasing the evaluation time can be accumulated according to the previous method.

At S10, the number of times the misfire evaluation time threshold value is updated to increase is recorded using the counter c, and the number of times the misfire evaluation time threshold value is updated to decrease is recorded using the counter d.

S11, determining whether the misfire evaluation time threshold value is increased or decreased only when the condition is satisfied, specifically comparing the values of the counter c and the counter d:

if the value of the counter c is greater than the value of the counter d by more than a preset value G (12000 in this example), the misfire evaluation time threshold value is updated only to be allowed to be increased;

if the value of the counter c is smaller than the value of the counter d by more than a preset value H (12000 in this example), the misfire evaluation time threshold value is updated only to be allowed to be decreased;

if neither of the above conditions are met, the misfire evaluation time threshold update may be increased or decreased.

And S12, judging whether the misfire evaluation time is smaller than the misfire evaluation time threshold value, if so, judging that the engine has no misfire, and if not, judging that the engine has misfire.

Wherein the counters a, b, c, d and the misfire evaluation time threshold value can all be saved electrically.

Based on the same inventive concept, an embodiment of the present application further provides an electronic device, which includes a memory, a processor, and a computer program stored in the memory and running on the processor, and when the processor executes the computer program, all or part of the method steps of the method are implemented.

The second embodiment is basically the same as the first embodiment in principle and technical scheme, and the difference is as follows: attempting to enter misfire diagnosis after 6 items before the misfire diagnosis activation condition are met in the rotation speed mode, and terminating the misfire diagnosis if the engine rotation speed fluctuation exceeds a preset rotation speed (+ -15 rpm) after entering the misfire diagnosis; and entering misfire diagnosis if the engine speed fluctuation does not exceed a preset speed (+ -15 rpm) after entering the misfire diagnosis.

The third embodiment is basically the same as the first embodiment in principle and technical scheme, and the difference is as follows: after step S8, it is judged that the misfire evaluation time threshold value updating condition is satisfied, and the misfire evaluation time threshold value is updated only if satisfied, otherwise the misfire evaluation time threshold value is not updated.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.